This invention relates to a method and apparatus for the use of certain crystalline phosphor compositions in the laser field. The term "phosphor compositions" herein refers to compositions that convert energy into electromagnetic radiation of desired wavelength. The term "laser" means light amplification by stimulated emission of radiation. More particularly, this invention relates to certain crystalline phosphor compositions which are suitable for use as an optical convertor in a laser cavity system, for example, a laser system using a lasing host material such as yttrium aluminium garnet (Y.sub.3 Al.sub.5 O.sub.12), known as "YAG". In general, the crystalline optical convertor is used to absorb input electromagnetic radiation not normally absorbed by the lasing ion and convert it to a wavelength which is more readily usable by optically active lasing ions, such as neodymium ions (Nd.sup.3.sup.+), in the laser system. More specifically, when the lasing ions are neodymium ions (Nd.sup.3.sup.+), the crystalline optical convertor changes electromagnetic energy having a wavelength of less than about 4000 A. to electromagnetic energy having a wavelength between about 5500 A. and 8500 A., where A. indicates Angstrom units.
Solid-state laser systems of the prior art are inefficient energy convertors because much of the input electromagnetic radiation does not have the same wavelength as the pumpband of the laser rod material. Therefore, it is desirable to find a way to compress the broad-band input radiation into a relatively narrow band of wavelengths that match the pumpband of the laser rod. Optical convertors for the laser cavity have been known in the prior art, but they have not been very successful heretofore. Most of the optical convertors known in the art have been organic materials. Even these have been used only for certain specific cases. Most of the solid state laser systems use neodymium (Nd.sup.3.sup.+) ions incorporated in a suitable matrix to form a laser rod. The organic optical convertors of the prior art are nearly useless when the lasing ions are neodymium (Nd.sup.3.sup.+) ions.
Laser cavity systems consist of three main components: the laser rod, the pump lamps, and an internal parabolic reflecting surface for focussing the pump light on the laser rod to cause the neodymium (Nd.sup.3.sup.+) ion to emit coherent light in a laser beam. Coherent light refers to an organization of energy waves emitted by a stimulated atom so that they travel in the same direction, at the same frequency, and perfectly in step with the stimulating radiation.